CN118160325A

CN118160325A - Acoustic transducer with improved low frequency response

Info

Publication number: CN118160325A
Application number: CN202280072144.0A
Authority: CN
Inventors: R·J·利特尔
Original assignee: Qualcomm Technologies Inc
Current assignee: Qualcomm Technologies Inc
Priority date: 2021-11-09
Filing date: 2022-11-09
Publication date: 2024-06-07
Also published as: US20230143656A1

Abstract

Aspects of an acoustic transducer are described. One aspect is a microelectromechanical (MEMS) transducer that includes a substrate and a plurality of cantilever beams. The first cantilever beam includes a first protrusion and a first piezoelectric structure, wherein the first piezoelectric structure includes a first deflection end and a first fixed end, wherein the first fixed end is coupled to the substrate, and wherein the first deflection end is suspended away from the substrate. The first cantilever beam is separated from the second cantilever beam by a gap. The first protrusion is disposed at the first deflection end and increases a thickness of the first cantilever beam along the gap at the first deflection end. The second projection of the second beam is disposed at the second deflection end and increases the thickness of the second cantilever beam along the gap at the first deflection end.

Description

Acoustic transducer with improved low frequency response

Technical Field

The present disclosure relates generally to acoustic transducers, and more particularly to piezoelectric microelectromechanical system (MEMS) acoustic transducers with improved low frequency response.

Background

MEMS technology has made it possible to use wafer deposition techniques to develop smaller microphones and other acoustic transducers. In general, MEMS microphones may take various forms including, for example, capacitive microphones and piezoelectric microphones. Piezoelectric MEMS microphones can provide various advantages. For example, a piezoelectric MEMS microphone may not require a backplate, which eliminates squeeze film damping (an inherent noise source of capacitive MEMS microphones). Furthermore, piezoelectric MEMS microphones are reflow compatible and can be mounted to a Printed Circuit Board (PCB) using a lead-free solder process, which can cause irreparable damage to other types of microphones. These and other advantages may be more fully achieved by an improved piezoelectric MEMS microphone, for example, which is capable of addressing high noise floor and improving microphone sensitivity.

Disclosure of Invention

Various implementations of systems, methods, and devices within the scope of the appended claims have several aspects, none of which are solely responsible for the desirable attributes described herein. Without limiting the scope of the appended claims, some prominent features are described herein. Aspects described herein include devices, wireless communication apparatus, circuits, and modules that support piezoelectric MEMS transducers.

One aspect is a microelectromechanical (MEMS) transducer. The MEMS transducer includes: a substrate; a first cantilever beam comprising a first protrusion and a first piezoelectric structure, wherein the first piezoelectric structure comprises a top surface, a bottom surface, a first side, a first end coupled to the substrate, and a second end suspended away from the substrate and the first end; and a second cantilever beam comprising a second protrusion and a second piezoelectric structure, wherein the second piezoelectric structure comprises a top surface, a bottom surface, a first side, a first end coupled to the substrate, and a second end suspended away from the substrate and the first end; wherein the first cantilever beam is positioned adjacent to the second cantilever beam and separated by a gap between the first side of the first piezoelectric structure and the first side of the second piezoelectric structure, wherein a corner of the first end of the first cantilever beam coupled to the substrate is separated from a corner of the first end of the second cantilever beam coupled to the substrate by an initial gap distance, wherein the first side of the first piezoelectric structure and the first side of the second piezoelectric structure are separated by the gap distance; wherein the first protrusion is positioned along the gap along a top first side edge of the first cantilever beam on a top or bottom surface of the first piezoelectric structure at the second end of the first piezoelectric structure; and wherein the second protrusion is positioned along the gap along a top first side edge of the second cantilever beam on the top surface or the bottom surface at the second end of the second piezoelectric structure.

Another aspect is a method. The method comprises the following steps: manufacturing a first piezoelectric structure of a first cantilever beam and a second piezoelectric structure of a second cantilever beam by using a piezoelectric layer on a substrate; and fabricating a first protrusion on the first piezoelectric structure and a second protrusion on the second piezoelectric structure; wherein the first cantilever beam comprises a first protrusion in the piezoelectric layer and a first piezoelectric structure, wherein the first piezoelectric structure comprises a first deflection end and a first fixed end, wherein the first fixed end is coupled to the substrate, wherein the first deflection end is suspended away from the substrate; wherein the second cantilever beam comprises a second protrusion in the piezoelectric layer and a second piezoelectric structure, wherein the second piezoelectric structure comprises a second deflection end and a second fixed end, wherein the second fixed end is coupled to the substrate, wherein the second deflection end is suspended away from the substrate; wherein the first cantilever beam and the second cantilever beam are separated by a gap; wherein the first protrusion is disposed at the first deflection end and increases a thickness of the first cantilever beam along the gap at the first deflection end; and wherein the second protrusion is disposed at the second deflection end and increases the thickness of the second cantilever beam along the gap at the first deflection end.

Another aspect is a microelectromechanical (MEMS) transducer. The MEMS transducer includes: a substrate; a first cantilever beam comprising a first protrusion and a first piezoelectric structure, wherein the first piezoelectric structure comprises a first deflection end and a first fixed end, wherein the first fixed end is coupled to the substrate, and wherein the first deflection end is suspended away from the substrate; a second cantilever beam comprising a second protrusion and a second piezoelectric structure, wherein the second piezoelectric structure comprises a second deflection end and a second fixed end, wherein the second fixed end is coupled to the substrate, and wherein the second deflection end is suspended away from the substrate; wherein the first cantilever beam and the second cantilever beam are separated by a gap; wherein the first protrusion is disposed at the first deflection end and increases a thickness of the first cantilever beam along the gap at the first deflection end; and wherein the second protrusion is disposed at the second deflection end and increases the thickness of the second cantilever beam along the gap at the first deflection end.

Some such aspects are configured wherein the first piezoelectric structure is disposed in a plane of the piezoelectric layer and is configured to deflect away from the plane of the piezoelectric layer at the first deflection end in response to acoustic vibrations on the first cantilever; and the second piezoelectric structure is disposed in a plane of the piezoelectric layer and is configured to deflect away from the plane of the piezoelectric layer at the second deflection end in response to acoustic vibrations on the second cantilever beam.

Some such aspects further include an acoustic port configured to provide an acoustic path from outside the MEMS transducer to the first cantilever and the second cantilever.

Some such aspects are configured wherein the first protrusion is disposed on a top surface of the first piezoelectric structure, the top surface being parallel to the plane of the piezoelectric layer on a side of the plane of the piezoelectric layer opposite the acoustic port.

Some such aspects are configured wherein the first protrusion extends less than one third of the distance from the first deflection end toward the substrate.

Some such aspects are configured wherein the first protrusion covers a surface of the first piezoelectric structure at the first deflection end of the first piezoelectric structure.

Some such aspects are configured wherein the first protrusion covers a contour of a surface of the first piezoelectric structure at the first deflection end of the first piezoelectric structure.

Some such aspects are configured wherein the first cantilever beam further comprises: a first electrode layer disposed on a top surface of the first fixed end of the first piezoelectric structure; and a second electrode layer disposed on a bottom surface of the first fixed end of the first piezoelectric structure, wherein the bottom surface is parallel to a top surface of the first fixed end of the first piezoelectric structure at an opposite side of the first piezoelectric structure.

Some such aspects are configured wherein the first electrode layer and the second electrode layer extend less than two-thirds of the distance from the first fixed end to the first deflection end.

Some such aspects are configured wherein the first protrusion is disposed on a bottom surface of the first piezoelectric structure, the bottom surface being parallel to the plane of the piezoelectric layer on a same side of the plane of the piezoelectric layer as the acoustic port, and wherein the first piezoelectric structure is fabricated in the plane of the piezoelectric layer.

Some such aspects further include a third cantilever beam comprising a third protrusion and a third piezoelectric structure, wherein the third piezoelectric structure comprises a third deflection end and a third fixed end, wherein the third fixed end is coupled to the substrate, wherein the third deflection end is suspended away from the substrate; wherein the gap has an initial gap distance between the first fixed end and the second fixed end, and wherein the gap has a gap distance that varies based on a length along the gap away from the substrate; wherein the first cantilever is separated from the third cantilever by a second gap, wherein the second gap has an initial gap distance between the first fixed end and the third fixed end, and wherein the second gap has a second gap distance that varies based on a second length along the second gap away from the substrate, a deflection position of the first cantilever, and a deflection position of the third cantilever; and wherein the first protrusion further increases the thickness of the first cantilever beam at the first deflection end along the second gap.

Some such aspects further include a plurality of cantilevers, each cantilever including a corresponding protrusion and a corresponding piezoelectric structure, wherein each corresponding piezoelectric structure includes a corresponding deflection end and a corresponding fixed end, wherein each cantilever of the plurality of cantilevers is separated from a first adjacent cantilever by a first corresponding gap and from a second adjacent cantilever by a second corresponding gap.

The foregoing and other features and embodiments will become more apparent by reference to the following description, claims and accompanying drawings.

Drawings

Fig. 1A illustrates an example of an acoustic transducer in accordance with aspects described herein.

Fig. 1B illustrates elements of an acoustic transducer according to aspects described herein.

Fig. 1C is a perspective view of a portion of a piezoelectric transducer according to embodiments described herein.

Fig. 1D illustrates a perspective view of an acoustic transducer in accordance with aspects described herein.

Fig. 1E illustrates elements of an acoustic transducer according to aspects described herein.

FIG. 2A illustrates a model of deflection of a cantilever beam in accordance with aspects described herein.

FIG. 2B illustrates elements of a model of deflection of a cantilever beam according to aspects described herein.

Fig. 2C illustrates elements of a model of deflection of a cantilever beam in accordance with aspects described herein.

FIG. 3 illustrates a graph of deflection of two adjacent cantilevered beams along a distance away from a fixed end toward a deflection end in accordance with aspects described herein.

Fig. 4A-4D illustrate example acoustic transducers with improved gap control geometry in accordance with aspects described herein.

Fig. 5A-5D illustrate example acoustic transducers with improved gap control geometry in accordance with aspects described herein.

Fig. 6A-6D illustrate example acoustic transducers with improved gap control geometry in accordance with aspects described herein.

Fig. 7A-7D illustrate example acoustic transducers with improved gap control geometry in accordance with aspects described herein.

Fig. 8A-8D illustrate example acoustic transducers with improved gap control geometry in accordance with aspects described herein.

Fig. 9 illustrates an example process for manufacturing an acoustic transducer in accordance with aspects described herein.

Fig. 10 illustrates a method associated with a MEMS acoustic transducer in accordance with aspects described herein.

FIG. 11 illustrates a computing device integrated with a MEMS acoustic transducer in accordance with aspects described herein.

Like reference symbols in the various drawings indicate like elements.

Detailed Description

The detailed description set forth below in connection with the appended drawings is intended as a description of exemplary aspects and implementations and is not intended to represent the only implementations in which the present invention may be practiced. The detailed description includes specific details for providing a thorough understanding of example aspects and implementations. In some cases, some devices are shown in block diagram form. Common drawing elements in the following figures may be identified using the same reference numerals.

Aspects described herein include piezoelectric microelectromechanical system (MEMS) acoustic transducers. Such acoustic transducers convert acoustic energy into electrical signals. One example of a MEMS acoustic transducer is a MEMS microphone that converts sound pressure into a voltage. The MEMS acoustic transducer as described herein may be composed of a cantilever beam above the air bag and surrounding the air bag to a large extent such that the external space and the air bag are separated by the beam of the MEMS acoustic transducer. When the cantilever Liang Jiyu is deflected by a change in air pressure, the air pressure differential between the air in the pocket and the air on the other side of the beam opposite the pocket (e.g., the outer region where the audio source produces air vibration or sound) produces an electrical signal in the piezoelectric MEMS transducer.

The gaps between the beams allow air to enter the pocket surrounded by the MEMS acoustic transducer from the outer region. Variations in the fabrication of the beams and variations in the deflection positions due to stresses in the beams may result in dimensional variations in the gaps between the different devices, which may affect the performance of the MEMS acoustic transducer. Residual stress in a MEMS transducer refers to stress that remains in a film (e.g., layer) after the film is deposited (e.g., on a silicon substrate). For example, a silicon wafer may be heated and a thin film may be deposited on the wafer at an elevated temperature, and then the wafer cooled back to room temperature (e.g., a lower temperature). If the thermal expansion coefficient of the film is different from that of silicon, the film will have residual stress at room temperature. Residual stress of sputtered films (e.g., certain piezoelectric layers according to aspects described herein) can be adjusted by adjusting deposition parameters. Such parameters may include gas pressure and deposition power. However, while the goal of the design and fabrication process is to make the cantilever beam horizontal (e.g., flat with respect to the substrate), device variations that may occur during the fabrication process may result in the piezoelectric MEMS transducer having residual stress characteristics to make the cantilever Liang Pianzhuai. Some piezoelectric MEMS microphones may suffer from a high noise floor due in part to the effects of residual stress. For example, in a microphone having a diaphragm that is constrained on all edges, residual stress can result in high diaphragm tension, resulting in reduced microphone sensitivity. In some cantilever designs, such as rectangular cantilever Liang Maike winds, residual stresses may cause the cantilever to bend away (e.g., up or down) from the substrate plane. Bending causes the gap between adjacent cantilevers to increase, thereby reducing acoustic impedance and causing an undesirable decrease in low frequency sensitivity. Aspects described herein include MEMS acoustic transducers having cantilever beams with gap control structures (e.g., gap control geometries) to reduce excessive gap variation between beams, thereby improving performance of the MEMS transducer device by reducing performance degradation due to such gaps.

Fig. 1A illustrates an example of an acoustic transducer in accordance with aspects described herein. Fig. 1A schematically illustrates a cross-sectional view of an acoustic sensor implemented as a MEMS transducer 10 (e.g., a MEMS microphone). As shown, the MEMS transducer 10 of fig. 1A includes a MEMS chip 112, which may include a die having a piezoelectric structure 114 (e.g., a cantilever or diaphragm for converting acoustic pressure into an electrical signal), and an application specific integrated circuit chip 116 for buffering and amplifying the electrical signal generated by the MEMS chip 112. The MEMS chip 112 and ASIC chip 116 are electrically connected by wire bonds 118 and mounted within the internal cavity of the package (although other packaging and connection techniques are possible). The package has a cover 128 and a substrate 122 (e.g., a printed circuit board). The printed circuit board and the MEMS substrate of the MEMS chip 112 form an acoustic port 124 for enabling acoustic pressure to access the piezoelectric structure(s) 114 of the MEMS chip 112. A plurality of pads 126 are provided on the bottom surface of the substrate 122 for solder connection of the MEMS transducer 10 as an element of an additional device. MEMS transducers may be used, for example, in cell phones, laptops, portable microphones, smart home accessories, or any other such device. The cover 128 may be used to form a housing for the microphone to provide an air pocket 123 that can provide one side of an air pressure differential that causes deflection and signal generation in the MEMS chip 112, and to mitigate electromagnetic interference (EMI).

As previously described, the MEMS chip 112 may be formed from one or more piezoelectric cantilevers or diaphragms (discussed below). The cantilever-based piezoelectric structure 114 provides the benefit of reducing die stress after the die is released during fabrication. On the other hand, the diaphragm structure of such a microphone chip 112 may require more stress control during manufacturing, as minimal residual stress within the diaphragm may result in significant sensitivity degradation. The plurality of cantilevers may be arranged to form a piezoelectric sensing structure (e.g., square, hexagonal, octagonal, or some other shape, as shown in fig. 1B, 4A-8D, etc., below).

Fig. 1A shows a structure with a MEMS chip 112 having an acoustic port 124 formed in a MEMS substrate. In other implementations, the MEMS substrate may be closed, with a pocket, similar to pocket 123 formed by a cavity below piezoelectric structure 114 and acoustic port 124 on the opposite side of piezoelectric structure(s) 114 from substrate 122. In other implementations, other such configurations of the acoustic port 124 may be used as long as there is a path for acoustic pressure to reach the piezoelectric structure 114.

Furthermore, some embodiments may implement both MEMS chip 112 and ASIC 116 as part of the same die, rather than implementing the system with two separate chips. Thus, discussion of separate chips is for illustration purposes. Furthermore, in other embodiments, the ASIC 116 may be implemented on a die in a separate package, with one or more interconnects electrically coupling the MEMS chip to the ASIC 116.

As shown in fig. 1A, a gap 106 exists between the piezoelectric structure(s) 114 of the MEMS chip. As described above, the variation in gap 106 may be caused by different deflections of the cantilever end of the piezoelectric structure (e.g., the end of the cantilever beam near gap 106), thereby causing variations in resonance characteristics and degrading device reliability and performance.

To counter the effects of gap variations between beams of MEMS chip 112 (e.g., variations in piezoelectric structure due to residual stress, manufacturing variations, etc.) on acoustic transducer performance, some transducer designs according to aspects described herein may include cantilever beam(s) having gap control geometry. Such gap control geometry in MEMS acoustic transducer designs may be referred to as protrusions added to the cantilever beam to increase the thickness of the beam, particularly around the deflection end of the beam at a location remote from Liang Fu to the substrate.

Fig. 1B illustrates an acoustic transducer 100 according to certain aspects of the present disclosure. In the example of fig. 1B, the acoustic transducer 100 includes four cantilever beams 102a, 102B, 102c, 102d (collectively, cantilever beams 102), each having a base 104a (e.g., a fixed end) that is fixed to a substrate (not shown, but similar to the MEMS substrate of the MEMS chip 112 of fig. 1A) and sides 104B, 104c that are unaffected by the substrate. The cantilevered beams 102a, 102b, 102c, and 102d each have a deflection end 190a, 190b, 190c, and 190d, a center 104d. Each beam may be a beam similar to beam 120 described below in fig. 1C, or a beam of fig. 4A-8D. During operation, the cantilever beam 102 moves (e.g., deflects) in the z-direction in and out of the x-y plane shown. The deflection is fixed at the outer edge attached to the substrate such that the gap distance between the corner edges of adjacent cantilever beams is static and greater at the deflection end 190 near the center 104d as each beam deflects as part of the vibration due to the acoustic vibration and associated pressure differential that occurs at the acoustic transducer 100. Each of the beams 102 may have a tendency to deflect upward or downward (e.g., the static deflection state may drift) when released from the substrate due to residual stresses, manufacturing variations, and other such effects. The center or rest deflection position or other deflection characteristics may be off-center due to manufacturing variations and may be off-design targets due to residual stresses on the material. However, the geometry of each beam 102 is such that the size of the gap 106 between the sides 104b, 104c of adjacent beams 102 remains small relative to, for example, the size of the gap between two facing rectangular cantilevers.

The size of the gap 106 is not always limited to or controlled by the separation distance between adjacent cantilever beams 102. Variations in the bridge 102 (e.g., due to material and manufacturing imperfections, etc.) may result in the bridge 102 potentially having different amounts of vertical deflection. The difference in vertical deflection position across adjacent cantilevers (sometimes referred to as vertical deflection mismatch) is undesirable because it increases the gap size between adjacent cantilevers, thereby reducing the acoustic resistance of the transducer and adversely affecting its low frequency response.

Fig. 1C is a perspective view of a portion 120 of a piezoelectric transducer according to embodiments described herein. Fig. 1C shows a single cantilever beam, which may be part of a larger acoustic transducer as described herein. The cantilever beams in section 120 are mounted on a substrate 137. In various implementations, the surface of the substrate 137 shown coupled to the cantilever beam may be a top surface, a bottom surface, or any other surface that allows the beam to be suspended over an acoustic port to allow acoustic waves to contact the beam and displace the beam based on a pressure differential on the opposite side of the cantilever beam. The cantilever beam in portion 120 has three electrode layers 136 separating portions of the piezoelectric material comprising the first piezoelectric structure. The cantilever beam has a first end 134 and a second end 132. The top surface visible in the perspective view of fig. 1C has a portion of the top surface two-thirds the way from the first end covered by one of the electrode layers 136. The second end 132 of the top surface is free of electrode material and is open such that a first protrusion (not shown) may be positioned along the first end 132 of the top surface first. The first side 135 faces the perspective view of fig. 1C, and the second side 130 (not visible) faces away from the perspective view of fig. 1C. The first end 134 is coupled to the substrate 137 and the second end 132 is suspended away from the substrate and the first end. The first side 135 and the second side 130 may be separated from adjacent cantilevers, respectively, having the same structure as the cantilever of fig. 1C. A plurality of such beams may be configured to enclose a symmetrical polygon, with each corresponding piezoelectric structure having the same triangular shape in a shared piezoelectric layer (e.g., piezoelectric acoustic transducers such as those of fig. 4A-4D, 5A-5D, 6A-6D, 7A-7D, 8A-8D, etc., combined to form the piezoelectric acoustic transducer). Each of the cantilever beams of such an acoustic transducer includes a cantilever beam separated from an adjacent beam by a gap between the sides, such as the beam of fig. 1C. In such a configuration, the first cantilever beam is positioned adjacent to the second cantilever beam and separated by a gap between the first side of the first piezoelectric structure and the first side of the second piezoelectric structure, wherein a corner of the first end of the first cantilever beam coupled to the substrate is separated from a corner of the first end of the second cantilever beam coupled to the substrate by an initial gap distance, wherein the first side of the first piezoelectric member is separated from the first side of the second piezoelectric structure by the gap distance. As will be described further below, in one implementation, a first protrusion (not shown) is positioned on the top or bottom surface of the first piezoelectric structure at the second end of the first piezoelectric structure along the gap along a top first side edge of the first cantilever beam, and a second protrusion is positioned on the top or bottom surface of the second piezoelectric structure at the second end of the second piezoelectric structure along the gap along a top first side edge of the second cantilever beam.

Such an acoustic transducer may include a cantilever beam of portion 120 and a second cantilever beam that includes a second protrusion (e.g., on a top surface of the beam, similar to second end 132 of the top surface of the beam of fig. 1C) and a second piezoelectric structure (e.g., similar to piezoelectric structure(s) between electrode layers 136 of the beam of fig. 1C). Such a second piezoelectric structure includes similar top and bottom surfaces, first and second sides, and first and second ends.

Fig. 1D illustrates a perspective view of an acoustic transducer in accordance with aspects described herein. Fig. 1D shows another configuration of a MEMS acoustic transducer having eight cantilever beams 140. Each cantilever beam 140 has a piezoelectric structure formed in a piezoelectric layer 143, wherein the structure of each of the eight cantilever beams 140 has an associated fixed end 141 and an associated deflection end 142. In some implementations, the stationary portion of the fixed end 141 is about 10 micrometers (μm) of a 400 micrometers (μm) long beam, with the remaining portion of the fixed end 141 bending with the free end based on the acoustic pressure applied across the cantilever beam 140. The eight cantilever beams 140 each have a similar triangular shape with a triangular base fixed to a substrate (not shown) at the end of the fixed end of each cantilever beam 140. Each cantilever beam 140 is positioned such that a side adjacent to a side of another of the cantilever beams is separated by a gap 106. The location of the eight cantilevers 140 with gaps 106 creates a symmetrical polygonal shape that is defined by a fixed base around the outside of the symmetrical polygon (e.g., octagons, with one exterior side for each of the cantilevers 140). In other aspects, other shapes may be used, such as square in fig. 1B. In other implementations, the MEMS acoustic transducer may include cantilever beams with different beam shapes for the same transducer, so long as the fixed outer edge attached to the substrate forms a closed transducer that separates air on one side (e.g., bag side similar to bag 123) from air on the other side (e.g., acoustic port side similar to acoustic port 124) using a gap (e.g., gap 106) between the cantilever beam (e.g., cantilever beam 140) and the beam. This separation allows the pressure differential between the sides of the MEMS transducer to apply a force to the beam and generate a signal that can be transmitted to the processing circuitry via bond pad 145.

As shown in fig. 1D, the cantilever beam has an associated length that is defined by a line segment from the tip of the deflection end 142 that is perpendicular to the fixed end of the fixed end 141. The line segment extends from the fixed end 141 at the substrate to the tip of the deflecting end 142. As described above, when acoustic vibrations occur at the surface of the deflection beam, the cantilever beam will move due to pressure (e.g., z-direction movement in and out of the x-y plane shown in fig. 1D). This in-plane and out-of-plane movement is referred to herein as vertical deflection. The deflection at the fixed end 141 will be less than the deflection at the deflection end 142, with the amount of deflection increasing toward the tip of the deflection end 142 along the distance of the line segment away from the substrate. The electrode that generates an electrical signal at bond pad 145 in response to acoustic vibrations on cantilever beam 140 may increase the stiffness of cantilever beam 140, and thus in some implementations, placement of the electrode may be limited to a space of about two-thirds of the line segment distance from the fixed attachment of the substrate at the fixed end toward the tip of deflection end 142 (e.g., limited to the fixed end). In some implementations, the electrode layer may cover the surface or x-y plane cross section of the entire illustrated fixed end 141 of each of the cantilever beams. In other implementations, a smaller electrode shape may be used in a portion of the fixed end 141 of each of the cantilevers 140. In some aspects, the deflection end 142 of each of the cantilevers does not include an electrode layer. The electrode layer does not extend to the tip of the free end 142 to avoid sensing free end movement in the deflected end (e.g., where the signal proportional to the stress in the cantilever is low). The protruding element may provide additional rigidity to the deflection end 142, which may improve proportional sensing of stress in the cantilever, while having additional rigidity at the fixed end 141. However, a larger vertical deflection at the deflection end 142 may result in a deflection mismatch, which may result in reduced performance, as described herein. Aspects described in further detail below may include protruding elements in the protruding layer of the deflecting end 142. When the vertical deflection mismatch between adjacent cantilevers becomes large enough that the airflow characteristics of gap 106 are affected (e.g., additional air is allowed to pass through gap 106) without additional thickness, the protruding elements increase the thickness of each cantilever along gap 106 to maintain the air resistance characteristics of gap 106.

Fig. 1E illustrates elements of an acoustic transducer according to aspects described herein. Fig. 1E shows a side view of the cantilevered beams 102C and 102D at a position without vertical offset, shown as offset 109 (e.g., with zero offset value or offset value not shown) across the gap 106 at the center 104D. As described above, during operation, the offset positions of the cantilever beams 102C and 102d may be matched due to similar acoustic forces on the beams, but in actual operation, differences in vertical deflection may result in a non-zero offset 109. Non-zero values of the offset 109 (e.g., as shown in fig. 2B) may be caused by manufacturing variations and residual stresses on the cantilever beams 102c, 102d as described above. As also shown, when the size of the gap 106 between adjacent beams becomes sufficient to change the air resistance through the gap 106, the large value of the offset 109 may cause performance degradation, thereby reducing the acoustic resistance of the transducer and negatively affecting its low frequency response.

Fig. 2A additionally shows a model 200 of an acoustic transducer having a geometry similar to the acoustic transducer 100, which may be affected by the offset 109 described above. In this example, the model 200 depicts the deflection experienced by four cantilever beams 202a, 202b, 202c, 202d, each having two 0.5 μm thick layers of aluminum nitride (AlN) stacked on top of each other. In this example, the residual stress of the bottom layer is 400MPa in the X-direction, 435MPa in the Y-direction, and the residual stress of the top layer is 400MPa in both the X-direction and the Y-direction. Thus, two pairs of opposing cantilever beams 202 (e.g., beams 202a and 202c and beams 202b and 202 d) have the same vertical deflection. However, the difference in residual stress in the X-direction and the Y-direction results in adjacent beams having different vertical deflections, which eventually enlarges the gap between adjacent beams. The offset between the deflection end 290c of the cantilever beam 202c and the deflection end 290 of the cantilever beam 202d is shown below.

Fig. 2B illustrates a model of deflection offset 207 of cantilever beams 202c, 202d according to aspects described herein. As mentioned above, the tip of the deflecting end of the cantilever beam moves much more in the z-direction than the rest of the cantilever beam. Due to the geometry of the MEMS acoustic device, the offset that may occur in the cantilever beam has a greater effect at the tip of the deflection end. Fig. 2B shows deflection ends 290c, 290d of corresponding cantilevers 202c, 202 d. Each of the cantilevers 202c, 202d has a thickness 209 and when the vertical mismatch offset 207 is large enough relative to the size of the gap 206 and the value of the thickness 209 to affect the air resistance through the gap 206 (e.g., where the gap 206 at the maximum offset 207 is significantly larger than the gap 206 without the offset 207), the performance of the MEMS acoustic transducer is degraded.

Fig. 2C illustrates a model of deflection offset 207 of cantilever beams 202C, 202d with added protrusions 292C, 292d, according to aspects described herein. As shown, the protrusions 292c, 292d that increase along the gap 206 maintain the gap distance relatively constant at the maximum offset 207, which prevents the performance degradation described above. As described above, the gap distance (e.g., initial gap distance) when adjacent cantilever beams are attached to a shared substrate will remain largely fixed due to the attachment to the substrate. When the cantilever beam extends from the substrate to the deflection end (e.g., free end), the gap distance will increase when there is a vertical deflection mismatch.

Fig. 3 shows a graph 300 illustrating modeled vertical deflection of two adjacent cantilever beams (e.g., similar to the examples of fig. 2A, 2B, and 2C). In this example, curve 302 depicts the vertical deflection of a first cantilever beam (e.g., beam 202 a) along the length of a gap between the first cantilever beam and an adjacent second cantilever beam (e.g., beam 202 b). Curve 304 depicts the vertical deflection of the second cantilever along the length of the gap between the first and second cantilevers. The fixed end of the cantilever beam is largely fixed in place when a vertical offset deflection occurs, where the offset is determined during manufacture. The vertical offset results from the beams having a small angle or deflection exiting the x-y plane and entering the z plane. Along a beam with vertical deflection, the deflection value increases along the length of the beam from a fixed end attached to the support substrate to the tip of the beam at the deflected end. As can be seen from a comparison of the curves 302, 304, in the example of fig. 3, the gap between two adjacent cantilever beams increases along the length, reaching a maximum of about 15 μm at the tip of the respective beam.

To reduce the effects of vertical deflection mismatch, the techniques described herein provide an acoustic transducer with a cantilever beam of improved gap control geometry. In particular, each cantilever beam may include a protrusion (e.g., protrusions 292c, 292 d) disposed on the piezoelectric structure, with the increased protrusion being sized to increase the thickness of the beam along at least a portion of the beam adjacent to another beam. By increasing the thickness of the beams in this way, the size of the gap between adjacent beams due to vertical deflection mismatch can be reduced relative to the size of the gap independent of the protrusions. Thus, the techniques described herein improve the performance of the transducer by, for example, more precisely controlling the size of the gap between adjacent beams, thereby improving the acoustic impedance and low frequency response (e.g., low frequency roll-off or-3 dB frequency) of the transducer. The protrusion 292 may be created by depositing material along the cantilever beam 202, for example, at the deflection end 290. The projection 292 may cover the entire deflection end 290 (e.g., as shown in fig. 8B), the profile of the deflection end 290 (e.g., as shown in fig. 7B), or a portion of the deflection end proximate to the gap (e.g., as shown in fig. 4B, 5B, and 6B). The protrusions may be formed by depositing material at the deflection end 290 of the beam 202, removing (e.g., etching) material from the deflection end 290 of the beam 202, or a combination of such fabrication processes. In general, the protrusions 292 may be formed using any suitable material, including metal, silicon nitride (Si ₃N₄), silicon (Si), polysilicon, or a combination of Si ₃N₄ and Si, among others.

Fig. 4A-4D illustrate examples of an acoustic transducer 400 according to one aspect of the present disclosure. In this example, the acoustic transducer 400 includes a plurality of cantilever beams 402 configured to convert acoustic pressure into an electrical signal. For example, the acoustic transducer 400 may be a MEMS acoustic transducer such as a microphone, and each cantilever beam 402 may include at least one piezoelectric layer disposed between two electrode layers. The piezoelectric layer may be used to convert an applied acoustic pressure into an electrical signal (e.g., voltage), and the electrode layer may be used to transmit the generated electrical signal to another component, such as an amplifier or an integrated circuit. In some examples, the piezoelectric layer includes aluminum nitride (AlN), lead zirconate titanate (PZT), zinc oxide (ZnO), polyvinylidene fluoride (PVDF), lead-magnesium-lead niobate-titanate (PMN-PT), or a combination thereof, among other piezoelectric materials. The electrode layer may include molybdenum (Mo), titanium (Ti), aluminum (Al), or platinum (Pt), or a combination thereof, as well as other suitable electrode materials. It should be noted that although the present discussion is in the context of piezoelectric acoustic transducers, the techniques described herein may be applied to any other suitable transducer that is subject to a stress cantilever.

Generally, each cantilever beam 402 includes a fixed end 404a, sides 404b, 404c, and a free end 404d (e.g., a deflection end). At least a portion of the fixed end 404a may be coupled to the substrate 406, while the remainder of the cantilever beam 402 (including the sides 404b, 404c and the free end 404 d) may be substantially separated from the substrate 406. Preferably, each of the sides 404b, 404c of a given cantilever beam 402 is parallel to the corresponding sides 404b and 404c of an adjacent beam 402 and separated by a gap 408. The size of the gap 408 may be set during manufacture and may be selected based on, for example, the desired acoustic impedance and/or low frequency response (e.g., 85Hz ± 15 Hz) of the transducer 400. In some examples, the gap 408 between adjacent cantilever beams 402 is fabricated to be about 1 μm. The size of the gap 408 between adjacent cantilever beams 402 is preferably maintained (e.g., 1 μm) after fabrication, but may increase due to deformation of the beams 402 caused by residual stress. In addition, manufacturing variations and residual stress variations between different cantilever beams and across beams in different devices may be tested to identify statistical properties associated with the design. For example, such variations may vary within a wafer as well as from wafer to wafer. Wafer level and device level testing may be used to determine whether individual devices meet target performance characteristics (e.g., low frequency roll-off or-3 dB frequency characteristics). For example, the manufacturing and performance analysis of the design may test the devices to determine a selected standard deviation value or another threshold tolerance to identify a threshold number or percentage of devices that will have a vertical mismatch below a selected level. For example, the test may determine a six sigma (e.g., 99.99966%) vertical mismatch value, where most MEMS acoustic transducers of a given design will have a vertical mismatch below the identified value after a given period of time. The threshold design value may be used to select a protrusion geometry that will limit performance degradation of the MEMS acoustic transducer with a vertical deflection mismatch below the selected value. For example, if manufacturability and design testing determine a six sigma vertical mismatch value of 15 micrometers (μm), and a minimum protrusion of 8 micrometers along the top edge of the gap between the cantilevers in the design would limit the effect of 15 μm mismatch on the airflow through the gap, the geometry of the cantilevers can be designed with such protrusions. Other design considerations may include adjusting the thickness of the piezoelectric layer and the addition of protrusions, placement of electrodes to affect the stiffness of the cantilever beams, the width of the protrusions, and whether the protrusions will cover the entire surface at the free end (e.g., the top surface of deflection) of each cantilever beam (e.g., affect the mass and resonant frequency of the beam in response to impinging acoustic waves), or other such design considerations. In some designs, standard bump thickness and width at the beam surface (e.g., top, bottom, etc. to increase the thickness of the beam) may be used, and performance testing and tuning may be performed based on actual or simulated device performance. For example, such standard thickness may be 30% of the thickness of the piezoelectric layer(s) of the cantilever beam, with a minimum width based on the protrusion geometry used in the available manufacturing process. In other examples, other thicknesses may be used (e.g., 40%, 15% of the protrusion, or a fixed target thickness value for a given design).

In some examples, the free end 404d of each cantilever beam 402 may have a width (e.g., an in-plane or X-Y plane width) that is substantially less than the width of the fixed end 404a such that the beam 402 tapers from the fixed end 404a to the free end 404 d. This arrangement may be achieved by each cantilever beam 402 having a substantially triangular geometry, although in some implementations other geometries (e.g., wedge-shaped geometries) may be used. As described above, such an arrangement generally helps mitigate the effect of residual stress on the size of the gap 408, but may not be particularly effective in maintaining the desired gap 408 in the presence of variations in residual stress of the bridge 402.

To prevent the size of the gap 408 between adjacent cantilever beams 402 from increasing due to residual stress and/or the effects of vertical deflection mismatch, some or all of the beams 402 may include a protrusion 414 that increases the thickness 410 of at least a portion of the beam adjacent to another beam. For example, the protrusions 414 may increase the thickness 410 of the beam 402 along at least a portion of the sides 404b, 404c or the free end 404d, or both. In some examples, the thickness 410 of the portion of the beam 402 may be increased such that it is greater than the thickness 412 of at least a portion of the fixed end 404a of the respective beam. The protrusions 414 may be created by, for example, depositing material along a portion of the beam 402 adjacent to another beam, removing (e.g., etching) material from a portion of the beam 402, or a combination of these fabrication processes.

In general, the arrangement and size of the protrusions 414 may be selected based on the needs of a particular implementation. In this example, the protrusions 414 form walls along the top perimeter of the free end 404d and a portion of the sides 404b, 404c of the beam 402. In this way, the protrusions 414 maintain a consistent size of the gap 408 between adjacent beams 402 while limiting increased mass and interference with the sensing area of the beams 402. In some examples, the thickness of the protrusions 414 is a target thickness (e.g., approximately 6 micrometers (μm), 4 μm, 8 μm, a thickness in a range between 2 μm and 15 μm, etc.), although different thicknesses may be used depending on the desired deflection of the cantilever beam 402. In some aspects, the thickness of the protrusions 414 may be set to a percentage, such as 30%, 10%, etc., of the thickness of the beam (e.g., piezoelectric layer). In some aspects, the thickness may be set based on testing and deflection mismatch of the fabricated devices, where the thickness of the protrusions 414 is selected to limit the number of devices that do not meet performance targets due to deflection mismatch of residual stresses. In general, the protrusions 414 may be formed using any suitable material, including metal, silicon nitride (Si ₃N₄), silicon (Si), polysilicon, or a combination of Si ₃N₄ and Si, or the like.

Fig. 4A-4D illustrate aspects of one implementation of a MEMS acoustic transducer 400. The perspective views of fig. 4A-4D show adjacent cantilever beams 402 separated by gap(s) 408. Fig. 4D shows a detail of each cantilever beam 402, and fig. 4A shows adjacent cantilever beams 402A and 402B. The acoustic transducer 400 includes a substrate 406, a first cantilever beam that includes a first piezoelectric structure 405 and a first protrusion 414 (e.g., a portion of the protrusion on a top surface of the first beam 402A). The piezoelectric structure has a first fixed end 403 and a first free end 404, wherein the first fixed end 403 is coupled to a substrate 406 and the first deflection end 404 is suspended away from the substrate 406. As described above in fig. 1C, the piezoelectric structure may be a piezoelectric material having any number of electrode layers integrated with the piezoelectric structure 105 or coupled to the piezoelectric structure 105. Fig. 4A-4D, 5A-5D, 6A-6D, 7A-7D, and 8A-8D do not show electrode layers, but there are such layers to allow for conversion of acoustic pressure to electrical signals.

The adjacent second cantilever beam 402B similarly has a second protrusion 414 (e.g., a portion of the protrusion 414 on the top surface of the cantilever beam 402B) and a second piezoelectric structure 405, wherein the second piezoelectric structure comprises a second deflection end 404 and a second fixed end 403, wherein the second fixed end is coupled to the substrate 406, and wherein the second deflection end 404 is suspended away from the substrate 406. As shown, the first cantilever beam 402A is separated from the second cantilever beam 402B by a gap 408, wherein a first protrusion 414 of the first cantilever beam 402A is disposed at the first deflection end 404 (e.g., as shown in fig. 4D), and a thickness 410 of the first cantilever beam is increased along the gap 408 at the first deflection end 404 (e.g., as compared to a thickness 412 at the fixed end 403). Similarly, a second protrusion 414 of second cantilever beam 402B is disposed at second deflection end 404 and increases thickness 410 of second cantilever beam 402B along gap 408 at second deflection end 404.

Fig. 4A is a plan view parallel to the plane of a piezoelectric layer as a layer including the piezoelectric structure 405. As described herein, the piezoelectric structure 405 of the cantilever beam 402 is configured to deviate from this plane (e.g., in and out in fig. 4A and 4B, and up and down in fig. 4C and 4D). The acoustic port 411 is part of an acoustic path that provides a path for acoustic pressure from outside the acoustic transducer 400 to between the cantilever beams 402. In fig. 4C and 4D, protrusions 414 are shown disposed on the top surface 413 of the piezoelectric structure 405. The illustrated protrusion 414 extends from the tip of the fixed end 403 to about half the length of the tip of the deflected (e.g., free) end 404. In other implementations, the protrusion extends less than one third of the length of the piezoelectric structure. In other aspects, the protrusions may be designed for specific performance impacts to limit the mass added to cantilever beam 402 while increasing strength and limiting the impact of deflection mismatch, as described herein.

The protrusions 414 of fig. 4B illustrate the protrusions 414 placed on the top surface 413 within a threshold distance of the gap(s) 408 on either side of the cantilever beam. Other projection arrangements are described below in fig. 5A-5D, 6A-6D, 7A-7D, and 8A-8D. As can be seen in fig. 4A, cantilever beam 402 and the combination of gaps 408 between cantilever beams 402 enclose a symmetrical polygon (e.g., an octagon).

Fig. 5A-5D, 6A-6D, 7A-7D, and 8A-8D illustrate various embodiments of an acoustic transducer according to an aspect of the present disclosure. Each of these acoustic transducers is substantially similar to acoustic transducer 400 described with reference to fig. 4A-4D, and for brevity, only these differences will be described. Referring to fig. 5A-5D, the acoustic transducer 500 includes a plurality of cantilevered beams 502, each having a protrusion 514 arranged to form a wall along a bottom perimeter of the free end 404D and a portion of the sides 404b, 404c of the beams 502 (e.g., the protrusions 514 are arranged in a plane intersecting a plane defined by the underlying substrate 406). In fig. 5A-5D, a protrusion 514 is provided on the bottom surface 513 of the piezoelectric structure 405. In some examples, the protrusions 514 may be created by etching the underlying substrate 406 instead of depositing additional layers on top of the cantilever beam 502 (as shown in fig. 4A-4D), and thus may reduce the manufacturing cost of the transducer 500. Referring to fig. 6A-6D, the acoustic transducer 600 includes a plurality of cantilevered beams 602, each having a protrusion 614 formed within the beam 602 and creating a wall along a top perimeter of the free end 404D and a portion of the sides 404b, 404c of the beam. Referring to fig. 7A-7D, the acoustic transducer 700 includes a plurality of cantilevered beams 702, each having a protrusion 714 that is similar to the protrusion 614 of the beam 602, but with the addition of a connecting member 716, for example, to increase the strength of the protrusion 714. Referring to fig. 8A-8D, the acoustic transducer 800 includes a plurality of cantilevered beams 802, each having a protrusion 814 similar to the protrusion 714 of the beam 702, but completely filled to form a solid rather than a wall. In some examples, the protrusion 814 may be easier to manufacture than, for example, the protrusion 714, but the greater total mass of the protrusion 814 may reduce the resonant frequency of the beam 802 (and thus the transducer 800).

Each of fig. 4A-4D, 5A-5D, 6A-6D, 7A-7D, and 8A-8D illustrate aspects of a MEMS acoustic transducer described herein. While the illustrated aspects specifically described herein include cantilever beams in a MEMS transducer, where each cantilever beam has the same pattern of protrusions on each cantilever beam, in some aspects adjacent beams may include different patterns of protrusions, or adjacent cantilever beams may include one beam with protrusions and another beam without protrusions.

Fig. 9 illustrates an exemplary process 900 for manufacturing an acoustic transducer in accordance with an aspect of the disclosure. At 902, alternating electrode layers and piezoelectric layers are deposited onto a substrate. In certain aspects, the first electrode layer is deposited on the substrate (or on the SiO2 layer deposited on the substrate). The first piezoelectric layer may be deposited on the first electrode layer. The second electrode layer may be deposited on the first piezoelectric layer. In this way, alternating electrode layers and piezoelectric layers are deposited onto the substrate. In some examples, a plurality of alternating electrode layers and piezoelectric material layers are deposited onto a substrate. For example, a second piezoelectric layer may be deposited on the second electrode layer. In addition, a third electrode layer may be deposited on the second piezoelectric layer. Thus, one or more electrode piezoelectric electrode compositions may be present.

At 904, a deposition layer is formed to define one or more cantilever beams having a gap control protrusion sized to increase a thickness of the beam along at least a portion of the beam adjacent to another beam. In some examples, the deposited layer is formed using an etching process. In other examples, other methods of formation may be used. In some examples, the deposited layer is formed to define at least a first cantilever beam and a second cantilever beam adjacent to the first beam. Each cantilever beam may include a piezoelectric layer disposed between a pair of electrode layers. Further, each cantilever beam may include a base attached to the substrate, a body and sides off of the substrate, and an end off of the substrate. In some examples, the free end of each cantilever beam may have a width (e.g., in-plane or X-Y plane width) that is much smaller than the width of the fixed end such that the beam tapers from the fixed end to the free end.

In some aspects, the protrusion is formed along at least a portion of each of the first and second beams adjacent to the other beam. For example, the protrusions may be formed along at least a portion of the body/side of the beam, the free end of the beam, or both. In some aspects, the protrusion is positioned less than a threshold distance from an edge of the beam near the gap. In some aspects, the protrusions may be formed in a layer of material, wherein a central portion of the protrusions is etched away to reduce the mass of the protrusions, thereby forming a contoured shape around the deflected end of the beam that is positioned along the gap edge and through the central portion of the beam (e.g., similar to protrusions 714 of fig. 7A-7D). In some aspects, the protrusions may be sized to increase the thickness of the beam along at least a portion of the beam. In some aspects, the thickness of the portion of the beam may be increased such that it is greater than the thickness of at least a portion of the fixed end of the respective beam. The protrusions may be made of material above or below the first and second cantilever beams. In some aspects, the protrusion may be located at a position associated with a vertical deflection mismatch between the first cantilever beam and the second cantilever beam. In some aspects, the size of the gap between the first and second cantilever beams is reduced to (or maintained at) the size of the manufacturing gap between the beams due to the protrusions. In this way, the gap between the first cantilever beam and the second cantilever beam may be reduced relative to the size of the gap between the first cantilever beam and the second cantilever beam independent of the protrusion.

Fig. 10 illustrates a method 1000 associated with a MEMS acoustic transducer in accordance with aspects described herein. In some aspects, the method is performed as part of a system configured for manufacturing a MEMS acoustic transducer (e.g., acoustic transducer 100, 400, 500, 600, 700, 800, etc.). In some aspects, method 1000 is implemented as computer readable instructions in a storage medium.

The method 1000 includes a block 1002. Block 1002 depicts operations for fabricating a first piezoelectric structure of a first cantilever and a second piezoelectric structure of a second cantilever using a piezoelectric layer on a substrate.

The method 1000 includes block 1004. Block 1004 depicts operations for fabricating a first protrusion on a first piezoelectric structure and fabricating a second protrusion on a second piezoelectric structure. Some such methods include block 1004, wherein the first cantilever beam includes a first protrusion in the piezoelectric layer and a first piezoelectric structure, wherein the first piezoelectric structure includes a first deflection end and a first fixed end, wherein the first fixed end is coupled to the substrate, wherein the first deflection end is suspended away from the substrate. Some such methods include block 1004, wherein the second cantilever beam includes a second protrusion in the piezoelectric layer and a second piezoelectric structure, wherein the second piezoelectric structure includes a second deflection end and a second fixed end, wherein the second fixed end is coupled to the substrate, wherein the second deflection end is suspended away from the substrate. Some such methods include block 1004, wherein the first cantilever beam is separated from the second cantilever beam by a gap. Some such methods include block 1004, wherein a first protrusion is disposed at the first deflection end and increases a thickness of the first cantilever beam along the gap at the first deflection end. Some such methods include block 1004, wherein a second protrusion is disposed at the second deflection end and increases a thickness of the second cantilever beam along the gap at the second deflection end.

Additional aspects may include methods and operations for fabricating devices having any of the structures described herein.

FIG. 11 is a diagram illustrating an example of a system for implementing certain aspects of the present technique. In particular, fig. 11 illustrates an example of a computing system 1100 that can include an acoustic transducer (e.g., a MEMS microphone) in accordance with aspects described herein. The acoustic transducers (e.g., MEMS transducer 11, acoustic transducer 400, etc.) may be integrated with any computing device, for example, constituting an internal computing system, a remote computing system, a camera, or any component thereof, where the components of the system communicate with each other using connection 1105. The connection 1105 may be a physical connection using a bus or a direct connection in the processor 1110, such as in a chipset architecture. The connection 1105 may also be a virtual connection, a networking connection, or a logical connection.

In some embodiments, computing system 1100 is a distributed system, where the functionality described in this disclosure may be distributed within a data center, multiple data centers, a peer-to-peer network, and the like. In some embodiments, one or more of the described system components represent a number of such components, each of which performs some or all of the functions of the described components. In some embodiments, the component may be a physical device or a virtual device.

The example system 1100 includes at least one processing unit (CPU or processor) 1110 and a connection 1105 communicatively coupling various system components including a system memory 1115, such as Read Only Memory (ROM) 1120 and Random Access Memory (RAM) 1125, to the processor 1110. Computing system 1100 can include a cache 1112 of memory directly connected to processor 1110, immediately adjacent to processor 1110, or integrated as part of processor 1110.

The processor 1110 may include any general purpose processor and hardware services or software services (such as services 1132, 1134, and 1136 stored in the storage device 1130, configured to control the processor 1110) as well as special purpose processors, wherein the software instructions are incorporated into the actual processor design. Processor 1110 may be essentially a completely independent computing system including multiple cores or processors, a bus, a memory controller, a cache, and so on. The multi-core processor may be symmetrical or asymmetrical.

To enable user interaction, computing system 1100 includes an input device 1145 that can represent any number of input mechanisms, such as a microphone (e.g., MEMS transducer 11, acoustic transducer 400, etc.) for voice or audio detection, and other input devices 1145, such as a touch-sensitive screen for gesture or graphical input, a keyboard, a mouse, motion input, voice, etc. Computing system 1100 can also include an output device 1135 that can be one or more of a number of output mechanisms. In some cases, the multi-mode system may enable a user to provide multiple types of input/output to communicate with computing system 1100.

Computing system 1100 can include a communication interface 1140 that can generally govern and manage user inputs and system outputs. The communication interface may perform or facilitate the reception and/or transmission of wired or wireless communications using wired and/or wireless transceivers, including reception and/or transmission using: audio port/plug, microphone port/plug, universal Serial Bus (USB) port/plug, apple ^TMLightning^TM port/plug, ethernet port/plug, fiber optic port/plug, dedicated wired port/plug, 3G, 4G, 5G, and/or other cellular data network wireless signaling, bluetooth ^TM wireless signaling, bluetooth ^TM low energy (BLE) wireless signaling, IBEACON ^TM wireless signaling, radio Frequency Identification (RFID) wireless signaling, near Field Communication (NFC) wireless signaling, dedicated Short Range Communication (DSRC) wireless signaling, 802.11 Fi wireless signaling, wireless Local Area Network (WLAN) signaling, visible Light Communication (VLC), worldwide Interoperability for Microwave Access (WiMAX), infrared (IR) communication wireless signaling, public Switched Telephone Network (PSTN) signaling, integrated Services Digital Network (ISDN) signaling, ad hoc network signaling, wireless signaling, microwave signaling, infrared signaling, visible light signaling, ultraviolet signaling, wireless signaling along the electromagnetic spectrum, or a combination thereof. The communication interface 1140 may also include one or more Global Navigation Satellite System (GNSS) receivers or transceivers for determining a location of the computing system 1100 based on receipt of one or more signals from one or more satellites associated with the one or more GNSS systems. GNSS systems include, but are not limited to, the Global Positioning System (GPS) in the united states, the russian global navigation satellite (GLONASS), the beidou navigation satellite system (BDS) in china, and the galileo global navigation satellite in europe. There is no limitation on the operation on any particular hardware arrangement, and therefore the basic features herein may be readily replaced by improved hardware or firmware arrangements that are developed.

The storage device 1130 may be a non-volatile and/or non-transitory and/or computer-readable Memory device, and may be a hard disk or other type of computer-readable medium, which may store computer-accessible data, such as magnetic cassettes, flash Memory cards, solid state Memory devices, digital versatile disks, magnetic cassettes, floppy disk, flexible disk, hard disk, magnetic tape, magnetic stripe/stripe, any other magnetic storage medium, flash Memory, memristor Memory, any other solid state Memory, compact disk read-only Memory (CD-ROM) optical disk, rewritable Compact Disk (CD) optical disk, digital Video Disk (DVD) optical disk, blu-ray disc (BDD) optical disk, holographic optical disk, another optical medium, secure Digital (SD) card, micro-secure digital (microSD) card, memoryCards, smart card chips, EMV chips, subscriber Identity Module (SIM) cards, mini/micro/nano/pico SIM cards, another Integrated Circuit (IC) chip/card, random Access Memory (RAM), static RAM (SRAM), dynamic RAM (DRAM), read Only Memory (ROM), programmable Read Only Memory (PROM), erasable Programmable Read Only Memory (EPROM), electrically Erasable Programmable Read Only Memory (EEPROM), flash memory EPROM (FLASHEPROM), cache memory (e.g., level 1 (L1) cache, level 2 (L2) cache, level 3 (L3) cache, level 4 (L4) cache, level 5 (L5) cache or other (l#) cache, resistive random access memory (RRAM/ReRAM), phase Change Memory (PCM), transfer torque RAM (STT-RAM), another memory chip or cartridge, and/or combinations thereof.

The storage 1130 may include software services, servers, services, etc., which when executed by the processor 1110, cause the system to perform functions. In some embodiments, the hardware services performing a particular function may include software components stored in a computer-readable medium in combination with hardware components (such as processor 1110, connection 1105, output device 1135, etc.) necessary to perform the function. The term "computer-readable medium" includes, but is not limited to, portable or non-portable storage devices, optical storage devices, and various other media capable of storing, containing, or carrying instruction(s) and/or data. Computer-readable media may include non-transitory media in which data may be stored and which do not include carrier waves and/or transitory electronic signals propagating wirelessly or through a wired connection. Examples of non-transitory media may include, but are not limited to, magnetic disks or tapes, optical storage media such as Compact Discs (CDs) or Digital Versatile Discs (DVDs), flash memory, or memory devices. The computer-readable medium may have code and/or machine-executable instructions stored thereon, which may represent procedures, functions, subroutines, programs, routines, subroutines, modules, software packages, classes, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted via any suitable means including memory sharing, message passing, token passing, network transmission, etc.

Specific details are provided in the above description to provide a thorough understanding of the embodiments and examples provided herein, but one skilled in the art will recognize that the application is not limited thereto. Thus, while illustrative embodiments of the application have been described in detail herein, it should be understood that the inventive concepts may be otherwise variously embodied and employed, and that the appended claims are intended to be construed to include such variations unless limited by the prior art. The various features and aspects of the above-described applications may be used alone or in combination. Moreover, embodiments may be utilized in any number of environments and applications beyond those described herein without departing from the broader scope of the specification. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. For ease of illustration, the method is described in a particular order. It should be understood that in alternative embodiments, the methods may be performed in a different order than that described.

For clarity of explanation, in some cases, the present technology may be represented as including individual functional blocks, including devices, device components, steps, or routines in methods that are embodied in software or a combination of hardware and software. Other components may be used in addition to those shown in the figures and/or described herein. For example, circuits, systems, networks, processes, and other components may be shown as block diagram form components in order not to obscure the embodiments in unnecessary detail. In other instances, well-known circuits, processes, algorithms, structures, and techniques may be shown without unnecessary detail in order to avoid obscuring the embodiments.

Furthermore, those of skill in the art will appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the aspects disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

Individual embodiments may be described above as a process or method, which is depicted as a flowchart, a flow diagram, a data flow diagram, a structure diagram, or a block diagram. Although a flowchart may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. Further, the order of the operations may be rearranged. The process terminates when its operation is completed, but there may be other steps not included in the figure. A process may correspond to a method, a function, a procedure, a subroutine, etc. When a process corresponds to a function, its termination may correspond to a function return call function or a main function.

The processes and methods according to the examples above may be implemented using computer-executable instructions stored or otherwise available from a computer-readable medium. For example, such instructions may include instructions and data which cause or otherwise configure a general purpose computer, special purpose computer, or processing device to perform a certain function or group of functions. Portions of the computer resources used may be accessible through a network. The computer-executable instructions may be, for example, binary files, intermediate format instructions, such as assembly language, firmware, source code. Examples of computer readable media that may be used to store instructions, information for use, and/or information created during a method according to the described examples include magnetic or optical disks, flash memory, USB devices provided with non-volatile memory, networked storage devices, and the like.

In some embodiments, the computer readable storage devices, media, and memory may comprise a cable or wireless signal comprising a bit stream or the like. However, when referred to, non-transitory computer-readable storage media expressly exclude media such as energy, carrier signals, electromagnetic waves, and signals themselves.

Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof, and in some cases may be partially dependent on the particular application, partially dependent on the desired design, partially dependent on the corresponding technology, and the like.

The various illustrative logical blocks, modules, and circuits described in connection with the aspects disclosed herein may be implemented or performed with hardware, software, firmware, middleware, microcode, hardware description languages, or any combination thereof, and may take any of a variety of form factors. When implemented in software, firmware, middleware or microcode, the program code or code segments (e.g., a computer program product) to perform the necessary tasks may be stored in a computer-readable or machine-readable medium. The processor(s) may perform the necessary tasks. Examples of form factors include notebook computers, smart phones, mobile phones, tablet devices or other small personal computers, personal digital assistants, rack-mounted devices, stand alone devices, and the like. The functionality described herein may also be embodied in a peripheral device or add-in card. As other examples, such functionality may also be implemented on a circuit board between different chips or different processes executing in a single device.

The instructions, the media for transmitting such instructions, the computing resources for executing such instructions, and other structures for supporting such computing resources are example means for providing the functionality described in this disclosure.

The techniques described herein may also be implemented in electronic hardware, computer software, firmware, or any combination thereof. Such techniques may be implemented in any of a variety of devices such as general purpose computers, wireless communication device handsets, or integrated circuit devices with multiple uses, including applications in wireless communication device handsets and other devices. Any features described as modules or components may be implemented together in an integrated logic device or separately as discrete but interoperable logic devices. If implemented in software, the techniques may be realized at least in part by a computer readable data storage medium comprising program code including instructions that when executed perform one or more of the methods, algorithms, and/or operations described above. The computer readable data storage medium may form part of a computer program product, which may include packaging material. The computer-readable medium may include memory or data storage media such as Random Access Memory (RAM), such as Synchronous Dynamic Random Access Memory (SDRAM), read-only memory (ROM), non-volatile random access memory (NVRAM), electrically erasable programmable read-only memory (EEPROM), flash memory, magnetic or optical data storage media, and the like. Additionally or alternatively, the techniques may be realized at least in part by a computer-readable communication medium that carries or communicates program code in the form of instructions or data structures and that can be accessed, read, and/or executed by a computer, such as a propagated signal or wave.

The program code may be executed by a processor, which may include one or more processors, such as one or more Digital Signal Processors (DSPs), general purpose microprocessors, application Specific Integrated Circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Such a processor may be configured to perform any of the techniques described in this disclosure. A general purpose processor may be a microprocessor; but, in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Thus, the term "processor" as used herein may refer to any of the foregoing structure, any combination of the foregoing structure, or any other structure or device suitable for implementation of the techniques described herein.

When a component is described as "configured to" perform a certain operation, such configuration may be achieved by designing electronic circuitry or other hardware to perform the operation, by programming programmable electronic circuitry (e.g., a microprocessor or other suitable electronic circuitry) to perform the operation, or any combination thereof.

The phrase "coupled to" or "communicatively coupled to" refers to any component that is directly or indirectly physically connected to another component, and/or any component that is directly or indirectly in communication with another component (e.g., connected to the other component through a wired or wireless connection and/or other suitable communication interface).

Many implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Other embodiments are within the scope of the following claims.

Illustrative aspects of the present disclosure include:

Aspect 1a microelectromechanical (MEMS) transducer comprising: a substrate; a first cantilever beam comprising a first protrusion and a first piezoelectric structure, wherein the first piezoelectric structure comprises a first deflection end and a first fixed end, wherein the first fixed end is coupled to the substrate, and wherein the first deflection end is suspended away from the substrate; a second cantilever beam comprising a second protrusion and a second piezoelectric structure, wherein the second piezoelectric structure comprises a second deflection end and a second fixed end, wherein the second fixed end is coupled to the substrate, and wherein the second deflection end is suspended away from the substrate; wherein the first cantilever beam is separated from the second cantilever beam by a gap; wherein the first protrusion is disposed at the first deflection end and increases a thickness of the first cantilever beam along the gap at the first deflection end; and wherein the second protrusion is disposed at the second deflection end and increases the thickness of the second cantilever beam along the gap at the first deflection end.

Aspect 2 the MEMS transducer of aspect 1, wherein: the first piezoelectric structure is disposed in a plane of a piezoelectric layer and is configured to deflect away from the plane of the piezoelectric layer at the first deflection end in response to acoustic vibrations on the first cantilever; and the second piezoelectric structure is disposed in the plane of the piezoelectric layer and is configured to deflect away from the plane of the piezoelectric layer at the second deflection end in response to acoustic vibrations on the second cantilever beam.

Aspect 3 the MEMS transducer of any of aspects 1 to 2, further comprising an acoustic port configured to provide an acoustic path from outside the MEMS transducer to the first cantilever and the second cantilever.

Aspect 4. The MEMS transducer of aspect 3, wherein the first protrusion is disposed on a top surface of the first piezoelectric structure, the top surface being parallel to a plane of the piezoelectric layer on a side of the plane of the piezoelectric layer opposite the acoustic port.

Aspect 5. The MEMS transducer of aspect 4 wherein the first protrusion extends less than one third of the distance from the first deflection end toward the substrate.

Aspect 6 the MEMS transducer of any of aspects 1 to 5, wherein the first protrusion is disposed on a bottom surface of the first piezoelectric structure, the bottom surface being parallel to a plane of the piezoelectric layer on the same side of the plane as the acoustic port, and wherein the first piezoelectric structure is fabricated in the plane of the piezoelectric layer.

Aspect 7 the MEMS transducer of any of aspects 1 to 5, wherein the first protrusion covers a surface of the first piezoelectric structure at the first deflection end of the first piezoelectric structure.

Aspect 8 the MEMS transducer of any of aspects 1 to 5 wherein the first protrusion covers a contour of a surface of the first piezoelectric structure at the first deflection end of the first piezoelectric structure.

Aspect 9 the MEMS transducer of aspect 8 wherein the first cantilever further comprises: a first electrode layer disposed on a top surface of the first fixed end of the first piezoelectric structure; and a second electrode layer disposed on a bottom surface of the first fixed end of the first piezoelectric structure, wherein the bottom surface is parallel to the top surface of the first fixed end of the first piezoelectric structure at an opposite side of the first piezoelectric structure.

Aspect 10 the MEMS transducer of any of aspects 3 to 9 wherein the first electrode layer and the second electrode layer extend less than two-thirds of the distance from the first fixed end to the first deflection end.

Aspect 11 the MEMS transducer of any of aspects 1 to 10, further comprising: a third cantilever beam comprising a third protrusion and a third piezoelectric structure, wherein the third piezoelectric structure comprises a third deflection end and a third fixed end, wherein the third fixed end is coupled to the substrate, wherein the third deflection end is suspended away from the substrate; wherein the gap has an initial gap distance between the first fixed end and the second fixed end, and wherein the gap has a gap distance that varies based on a length along the gap away from the substrate; wherein the first cantilever is separated from the third cantilever by a second gap, wherein the second gap has the initial gap distance between the first fixed end and the third fixed end, and wherein the second gap has a second gap distance that varies based on a second length along the second gap away from the substrate, a deflection position of the first cantilever, and a deflection position of the third cantilever; and wherein the first protrusion further increases the thickness of the first cantilever beam along the second gap at the first deflection end.

Aspect 12 the MEMS transducer of aspect 11 wherein the first protrusion is disposed on the top surface of the first piezoelectric structure at a location less than a threshold distance from the gap or the second gap.

Aspect 13 the MEMS transducer of any of aspects 1 to 12, further comprising a plurality of cantilever beams, each cantilever beam comprising a corresponding protrusion and a corresponding piezoelectric structure, wherein each corresponding piezoelectric structure comprises a corresponding deflection end and a corresponding fixed end, wherein each cantilever beam of the plurality of cantilever beams is separated from a first adjacent cantilever beam by a first corresponding gap and from a second adjacent cantilever beam by a second corresponding gap.

Aspect 14. The MEMS transducer of aspect 13 wherein the plurality of cantilever beams and associated gaps between the plurality of cantilever beams enclose a symmetrical polygon.

Aspect 15. The MEMS transducer of aspect 14 wherein each corresponding piezoelectric structure has the same triangular shape in the shared piezoelectric layer.

Aspect 16 the MEMS transducer of aspect 14 further comprising an acoustic port providing an acoustic path for sound from outside the MEMS transducer to propagate to the plurality of cantilever beams.

Aspect 17 the MEMS transducer of aspect 16 further comprising a pocket on a side of the plurality of cantilever beams opposite the acoustic port, wherein a pressure differential between a pressure of the pocket and a pressure of the acoustic port causes deflection of the plurality of cantilever beams and associated electrical signal generation.

The MEMS transducer of any of aspects 1 to 17 wherein the gap has an initial gap distance between the first and second fixed ends, and wherein the gap has a gap distance that varies based on a length along the gap away from a top surface of the substrate; wherein the initial gap distance is about 1 micrometer (μm), and wherein the gap distance at the tip of the first deflection end is about 15 μm.

Aspect 19 the MEMS transducer of any of aspects 1 to 18, wherein the thickness of the first protrusion and the thickness of the second protrusion are based on a change in deflection mismatch between the position of the first deflection end and the position of the second deflection end determined from manufacturing variations and material stresses of a MEMS transducer design of the MEMS transducer.

Aspect 20 the MEMS transducer of any of aspects 1 to 19 wherein the first and second cantilever beams each comprise an electrode layer, the MEMS transducer further comprising control circuitry coupled to the electrode layer and configured to process acoustic signals from acoustic deflections in the first and second cantilever beams.

Aspect 21. A method comprising: manufacturing a first piezoelectric structure of a first cantilever beam and a second piezoelectric structure of a second cantilever beam by using a piezoelectric layer on a substrate; and fabricating a first protrusion on the first piezoelectric structure and a second protrusion on the second piezoelectric structure; wherein the first cantilever beam comprises the first protrusion and the first piezoelectric structure in the piezoelectric layer, wherein the first piezoelectric structure comprises a first deflection end and a first fixed end, wherein the first fixed end is coupled to the substrate, wherein the first deflection end is suspended away from the substrate; wherein the second cantilever beam comprises the second protrusion in the piezoelectric layer and the second piezoelectric structure, wherein the second piezoelectric structure comprises a second deflection end and a second fixed end, wherein the second fixed end is coupled to the substrate, wherein the second deflection end is suspended away from the substrate; wherein the first cantilever beam is separated from the second cantilever beam by a gap; wherein the first protrusion is disposed at the first deflection end and increases a thickness of the first cantilever beam along the gap at the first deflection end; and wherein the second protrusion is disposed at the second deflection end and increases the thickness of the second cantilever beam along the gap at the first deflection end.

Aspect 22. The method of aspect 21, wherein: the first piezoelectric structure is disposed in a plane of the piezoelectric layer and is configured to deflect away from the plane of the piezoelectric layer at the first deflection end in response to acoustic vibrations on the first cantilever; and the second piezoelectric structure is disposed in the plane of the piezoelectric layer and is configured to deflect away from the plane of the piezoelectric layer at the second deflection end in response to acoustic vibrations on the second cantilever beam.

Aspect 23 the method of any one of aspects 21-22, further comprising fabricating an acoustic port configured to provide an acoustic path from an acoustic source to the first cantilever and the second cantilever, wherein the first protrusion is disposed on a top surface of the first piezoelectric structure, the top surface being parallel to a plane of the piezoelectric layer on a side of the plane of the piezoelectric layer opposite the acoustic port, and wherein the first protrusion extends less than one third of a distance from the first deflection end toward the substrate.

Aspect 24 the method of any one of aspects 21 to 23, further comprising: manufacturing a third cantilever beam comprising a third protrusion and a third piezoelectric structure, wherein the third piezoelectric structure comprises a third deflection end and a third fixed end, wherein the third fixed end is coupled to a top surface of the substrate, wherein the third deflection end is suspended away from the substrate, wherein the gap has an initial gap distance between the first fixed end and the second fixed end, and wherein the gap has a gap distance that varies based on a length along the gap away from the top surface, wherein the first cantilever beam is separated from the third cantilever beam by a second gap, wherein the second gap has the initial gap distance between the first fixed end and the third fixed end, and wherein the second gap has a second gap distance that varies based on a second length along the second gap away from the top surface, a deflection position of the first cantilever beam, and a deflection position of the third cantilever beam, and wherein the first protrusion further increases the thickness of the first cantilever beam along the second gap at the first deflection end.

The method of any one of aspects 21-24, further comprising fabricating a plurality of cantilever beams, each cantilever beam comprising a corresponding protrusion and a corresponding piezoelectric structure, wherein each corresponding piezoelectric structure comprises a corresponding deflection end and a corresponding fixed end, wherein each cantilever beam of the plurality of cantilever beams is separated from a first adjacent cantilever beam by a first corresponding gap and from a second adjacent cantilever beam by a second corresponding gap.

Aspect 26. The method of any one of aspects 21 to 25, wherein the plurality of cantilever beams and associated gaps between the plurality of cantilever beams enclose a symmetrical polygon, wherein each corresponding piezoelectric structure has the same triangular shape in the shared piezoelectric layer.

Aspect 27 the method of any one of aspects 21 to 26, further comprising fabricating a package comprising an acoustic port that provides an acoustic path for sound from an external sound source to propagate to the plurality of cantilever beams.

Aspect 28, a microelectromechanical (MEMS) transducer, comprising: a substrate; a first cantilever beam comprising a first protrusion and a first piezoelectric structure, wherein the first piezoelectric structure comprises a top surface, a bottom surface, a first side, a first end coupled to the substrate, and a second end suspended away from the substrate and the first end; and a second cantilever beam comprising a second protrusion and a second piezoelectric structure, wherein the second piezoelectric structure comprises a top surface, a bottom surface, a first side, a first end coupled to the substrate, and a second end suspended away from the substrate and the first end; wherein the first cantilever beam is positioned adjacent to the second cantilever beam and separated by a gap between the first side of the first piezoelectric structure and the first side of the second piezoelectric structure, wherein a corner of the first end of the first cantilever beam coupled to the substrate is separated from a corner of the first end of the second cantilever beam coupled to the substrate by an initial gap distance, wherein the first side of the first piezoelectric structure and the first side of the second piezoelectric structure are separated by a gap distance; wherein the first protrusion is positioned along the gap along a top first side edge of the first cantilever beam on the top surface or the bottom surface of the first piezoelectric structure at the second end of the first piezoelectric structure; and wherein the second protrusion is positioned along the gap along a top first side edge of the second cantilever beam on the top surface or the bottom surface at the second end of the second piezoelectric structure.

Aspect 29 the MEMS transducer of aspect 28, further comprising: a third cantilever beam comprising a third protrusion and a third piezoelectric structure, wherein the third piezoelectric structure comprises a third deflection end and a third fixed end, wherein the third fixed end is coupled to the substrate, wherein the third deflection end is suspended away from the substrate, wherein the gap has a gap distance that varies based on a length along the gap away from the top surface, wherein the first cantilever beam is separated from the third cantilever beam by a second gap, wherein the second gap has the initial gap distance between the first fixed end and the third fixed end, and wherein the second gap has a second gap distance that varies based on a second length along the second gap away from the top surface, a deflection position of the first cantilever beam, and a deflection position of the third cantilever beam, and wherein the first protrusion further increases the thickness of the first cantilever beam along the second gap at the first deflection end.

Aspects 28-29 the MEMS transducer of any of aspects 28-29 further comprising a plurality of cantilever beams, each cantilever beam comprising a corresponding protrusion and a corresponding piezoelectric structure, wherein each corresponding piezoelectric structure comprises a corresponding deflection end and a corresponding fixed end, wherein each cantilever beam of the plurality of cantilever beams is separated from a first adjacent cantilever beam by a first corresponding gap and from a second adjacent cantilever beam by a second corresponding gap, wherein the associated gaps between the plurality of cantilever beams and the plurality of cantilever beams enclose a symmetrical polygon, wherein each corresponding piezoelectric structure has the same triangular shape in a shared piezoelectric layer.

Aspect 31 the MEMS transducer of aspect 28, further comprising: a third cantilever beam comprising a third protrusion and a third piezoelectric structure; wherein the third piezoelectric structure comprises a top surface, a bottom surface, a first side, a first end coupled to the substrate, and a second end suspended away from the substrate and the first end; wherein the second end of the third cantilever is suspended away from the substrate and configured to deflect out of the plane of the piezoelectric layer in response to acoustic pressure; wherein the first cantilever beam is positioned adjacent to the third cantilever beam and separated by a gap between a second side of the first piezoelectric structure and the first side of the third piezoelectric structure, wherein a second corner of the first end of the first cantilever beam coupled to the substrate is separated from a corner of the first end of the third cantilever beam coupled to the substrate by a second gap distance.

The MEMS transducer of aspect 28 further comprising a plurality of cantilevers, each cantilever comprising a corresponding protrusion and a corresponding piezoelectric structure, wherein each corresponding piezoelectric structure comprises a corresponding second end suspended away from the substrate and a corresponding first end attached to the substrate, wherein each cantilever of the plurality of cantilevers is separated from a first adjacent cantilever by a first corresponding gap and from a second adjacent cantilever by a second corresponding gap, wherein the plurality of cantilevers and the associated gap between the plurality of cantilevers enclose a symmetrical polygon, wherein each corresponding piezoelectric structure has the same triangular shape in a shared piezoelectric layer.

Aspect 31, a microelectromechanical (MEMS) transducer, comprising: a substrate having a top; a first cantilever beam comprising one or more first portions, and a first protrusion, wherein the one or more first portions extend at a first vertical deflection relative to a plane of the top of the substrate; a second cantilever beam comprising one or more second portions, and a second protrusion, wherein the one or more second portions extend at a second vertical deflection relative to the plane of the top of the substrate; a gap between the first and second cantilevers, wherein a dimension of the gap varies based on a vertical deflection mismatch between the first and second cantilevers, wherein the first protrusion is positioned as part of a structure of the first cantilever along a portion of the gap to increase a thickness of the first cantilever along the gap; and a protrusion attached to the first cantilever beam or the second cantilever beam, the protrusion sized to reduce the size of the gap relative to a size of the gap independent of the protrusion.

Aspects 32 also include a plurality of cantilevers, each cantilever including a corresponding protrusion and a corresponding piezoelectric structure, wherein each corresponding piezoelectric structure includes a corresponding second end suspended away from the substrate and a corresponding first end attached to the substrate, wherein each cantilever of the plurality of cantilevers is separated from a first adjacent cantilever by a first corresponding gap and from a second adjacent cantilever by a second corresponding gap, wherein the plurality of cantilevers and the associated gap between the plurality of cantilevers enclose a symmetrical polygon, wherein each corresponding piezoelectric structure has the same triangular shape in a shared piezoelectric layer.

Aspect 33 a microelectromechanical (MEMS) transducer comprising means for providing improved low frequency response according to any aspect described herein.

Aspect 34. A method for manufacturing any of the MEMS transducers described herein.

Aspect 35 a storage medium includes instructions that, when executed by a system, cause the system to perform any of the operations described herein.

Claims

1. A microelectromechanical (MEMS) transducer, comprising:

A substrate;

a first cantilever beam comprising a first protrusion and a first piezoelectric structure, wherein the first piezoelectric structure comprises a first deflection end and a first fixed end, wherein the first fixed end is coupled to the substrate, and wherein the first deflection end is suspended away from the substrate;

A second cantilever beam comprising a second protrusion and a second piezoelectric structure, wherein the second piezoelectric structure comprises a second deflection end and a second fixed end, wherein the second fixed end is coupled to the substrate, and wherein the second deflection end is suspended away from the substrate;

wherein the first cantilever beam is separated from the second cantilever beam by a gap;

Wherein the first protrusion is disposed at the first deflection end and increases a thickness of the first cantilever beam along the gap at the first deflection end; and

Wherein the second protrusion is disposed at the second deflection end and increases the thickness of the second cantilever beam along the gap at the first deflection end.

2. The MEMS transducer of claim 1 wherein:

The first piezoelectric structure is disposed in a plane of a piezoelectric layer and is configured to deflect away from the plane of the piezoelectric layer at the first deflection end in response to acoustic vibrations on the first cantilever; and

The second piezoelectric structure is disposed in the plane of the piezoelectric layer and is configured to deflect away from the plane of the piezoelectric layer at the second deflection end in response to the acoustic vibration on the second cantilever.

3. The MEMS transducer of claim 1, further comprising an acoustic port configured to provide an acoustic path from outside the MEMS transducer to the first cantilever and the second cantilever.

4. A MEMS transducer as claimed in claim 3 wherein the first protrusion is provided on a top surface of the first piezoelectric structure, the top surface being parallel to the plane of the piezoelectric layer on a side of the plane of the piezoelectric layer opposite the acoustic port.

5. The MEMS transducer of claim 4 wherein the first protrusion extends less than one third of the distance from the first deflection end toward the substrate.

6. The MEMS transducer of claim 1 wherein the first protrusion covers a surface of the first piezoelectric structure at the first deflection end of the first piezoelectric structure.

7. The MEMS transducer of claim 1 wherein the first protrusion covers a contour of a surface of the first piezoelectric structure at the first deflection end of the first piezoelectric structure.

8. The MEMS transducer of claim 1 wherein the first cantilever beam further comprises:

A first electrode layer disposed on a top surface of the first fixed end of the first piezoelectric structure; and

And a second electrode layer disposed on a bottom surface of the first fixed end of the first piezoelectric structure, wherein the bottom surface is parallel to the top surface of the first fixed end of the first piezoelectric structure at an opposite side of the first piezoelectric structure.

9. The MEMS transducer of claim 8 wherein the first electrode layer and the second electrode layer extend less than two-thirds of the distance from the first fixed end to the first deflection end.

10. A MEMS transducer as claimed in claim 3 wherein the first protrusion is provided on a bottom surface of the first piezoelectric structure, the bottom surface being parallel to the plane of the piezoelectric layer on the same side of the plane of the piezoelectric layer as the acoustic port, and wherein the first piezoelectric structure is fabricated in the plane of the piezoelectric layer.

11. The MEMS transducer of claim 1 further comprising:

a third cantilever beam comprising a third protrusion and a third piezoelectric structure, wherein the third piezoelectric structure comprises a third deflection end and a third fixed end, wherein the third fixed end is coupled to the substrate, wherein the third deflection end is suspended away from the substrate;

Wherein the gap has an initial gap distance between the first fixed end and the second fixed end, and wherein the gap has a gap distance that varies based on a length along the gap away from the substrate;

wherein the first cantilever is separated from the third cantilever by a second gap, wherein the second gap has the initial gap distance between the first fixed end and the third fixed end, and wherein the second gap has a second gap distance that varies based on a second length along the second gap away from the substrate, a deflection position of the first cantilever, and a deflection position of the third cantilever; and

Wherein the first protrusion further increases the thickness of the first cantilever beam along the second gap at the first deflection end.

12. The MEMS transducer of claim 11 wherein the first protrusion is disposed on a top surface of the first piezoelectric structure at a location less than a threshold distance from the gap or the second gap.

13. The MEMS transducer of claim 1 further comprising a plurality of cantilevers, each cantilever comprising a corresponding protrusion and a corresponding piezoelectric structure, wherein each corresponding piezoelectric structure comprises a corresponding deflection end and a corresponding fixed end, wherein each cantilever of the plurality of cantilevers is separated from a first adjacent cantilever by a first corresponding gap and separated from a second adjacent cantilever by a second corresponding gap.

14. The MEMS transducer of claim 13 wherein the plurality of cantilever beams and associated gaps between the plurality of cantilever beams enclose a symmetrical polygon.

15. The MEMS transducer of claim 14 wherein each corresponding piezoelectric structure has the same triangular shape in a shared piezoelectric layer.

16. The MEMS transducer of claim 14 further comprising an acoustic port providing an acoustic path for sound from outside the MEMS transducer to propagate to the plurality of cantilever beams.

17. The MEMS transducer of claim 16 further comprising a pocket on a side of the plurality of cantilever beams opposite the acoustic port, wherein a pressure differential between a pressure of the pocket and a pressure of the acoustic port results in deflection of the plurality of cantilever beams and associated electrical signal generation.

18. The MEMS transducer of claim 1 wherein the gap has an initial gap distance between the first and second fixed ends, and wherein the gap has a gap distance that varies based on a length along the gap away from a top surface of the substrate;

Wherein the initial gap distance is about 1 micrometer (μm), and wherein the gap distance at the tip of the first deflection end is about 15 μm.

19. The MEMS transducer of claim 1 wherein the thickness of the first protrusion and the thickness of the second protrusion are based on a change in deflection mismatch between the position of the first deflection end and the position of the second deflection end, the deflection mismatch determined from manufacturing variations and material stresses for a MEMS transducer design of the MEMS transducer.

20. The MEMS transducer of claim 1 wherein the first and second cantilevers each include an electrode layer, the MEMS transducer further comprising control circuitry coupled to the electrode layer and configured to process acoustic signals from acoustic deflections in the first and second cantilevers.

21. A method, comprising:

manufacturing a first piezoelectric structure of a first cantilever beam and a second piezoelectric structure of a second cantilever beam by using a piezoelectric layer on a substrate; and

Fabricating a first protrusion on the first piezoelectric structure and a second protrusion on the second piezoelectric structure;

Wherein the first cantilever beam comprises the first protrusion and the first piezoelectric structure in the piezoelectric layer, wherein the first piezoelectric structure comprises a first deflection end and a first fixed end, wherein the first fixed end is coupled to the substrate, wherein the first deflection end is suspended away from the substrate;

Wherein the second cantilever beam comprises the second protrusion in the piezoelectric layer and the second piezoelectric structure, wherein the second piezoelectric structure comprises a second deflection end and a second fixed end, wherein the second fixed end is coupled to the substrate, wherein the second deflection end is suspended away from the substrate;

Wherein the second protrusion is disposed at the second deflection end and increases a thickness of the second cantilever beam along the gap at the first deflection end.

22. The method according to claim 21, wherein:

The first piezoelectric structure is disposed in a plane of the piezoelectric layer and is configured to deflect away from the plane of the piezoelectric layer at the first deflection end in response to acoustic vibrations on the first cantilever; and

23. The method of claim 21, further comprising fabricating an acoustic port configured to provide an acoustic path from an acoustic source to the first and second cantilevers, wherein the first protrusion is disposed on a top surface of the first piezoelectric structure, the top surface being parallel to a plane of the piezoelectric layer on a side of the plane of the piezoelectric layer opposite the acoustic port, and wherein the first protrusion extends less than one third of a distance from the first deflection end toward the substrate.

24. The method of claim 21, further comprising:

Manufacturing a third cantilever beam comprising a third protrusion and a third piezoelectric structure, wherein the third piezoelectric structure comprises a third deflection end and a third fixed end, wherein the third fixed end is coupled to a top surface of the substrate, wherein the third deflection end is suspended away from the substrate, wherein the gap has an initial gap distance between the first fixed end and the second fixed end, and wherein the gap has a gap distance that varies based on a length along the gap away from the top surface, wherein the first cantilever beam is separated from the third cantilever beam by a second gap, wherein the second gap has the initial gap distance between the first fixed end and the third fixed end, and wherein the second gap has a second gap distance that varies based on a second length along the second gap away from the top surface, a deflection position of the first cantilever beam, and a deflection position of the third cantilever beam, and wherein the first protrusion further increases the thickness of the first cantilever beam along the second gap at the first deflection end.

25. The method of claim 21, further comprising fabricating a plurality of cantilevers, each cantilever comprising a corresponding protrusion and a corresponding piezoelectric structure, wherein each corresponding piezoelectric structure comprises a corresponding deflection end and a corresponding fixed end, wherein each cantilever of the plurality of cantilevers is separated from a first adjacent cantilever by a first corresponding gap and separated from a second adjacent cantilever by a second corresponding gap.

26. The method of claim 25, wherein the plurality of cantilever beams and associated gaps between the plurality of cantilever beams enclose a symmetrical polygon, wherein each corresponding piezoelectric structure has the same triangular shape in a shared piezoelectric layer.

27. The method of claim 26, further comprising fabricating a package comprising an acoustic port that provides an acoustic path for sound from an external sound source to propagate to the plurality of cantilevers.

28. A microelectromechanical (MEMS) transducer, comprising:

A substrate;

a first cantilever beam comprising a first protrusion and a first piezoelectric structure, wherein the first piezoelectric structure comprises a top surface, a bottom surface, a first side, a first end coupled to the substrate, and a second end suspended away from the substrate and the first end; and

A second cantilever beam comprising a second protrusion and a second piezoelectric structure, wherein the second piezoelectric structure comprises a top surface, a bottom surface, a first side, a first end coupled to the substrate, and a second end suspended away from the substrate and the first end;

Wherein the first cantilever beam is positioned adjacent to the second cantilever beam and separated by a gap between the first side of the first piezoelectric structure and the first side of the second piezoelectric structure, wherein a corner of the first end of the first cantilever beam coupled to the substrate is separated from a corner of the first end of the second cantilever beam coupled to the substrate by an initial gap distance,

Wherein the first side of the first piezoelectric structure and the first side of the second piezoelectric structure are separated by a gap distance;

Wherein the first protrusion is positioned along the gap along a top first side edge of the first cantilever beam on the top surface or the bottom surface of the first piezoelectric structure at the second end of the first piezoelectric structure; and

Wherein the second protrusion is positioned along the gap along a top first side edge of the second cantilever beam on the top surface or the bottom surface at the second end of the second piezoelectric structure.

29. The MEMS transducer of claim 28 further comprising:

A third cantilever beam comprising a third protrusion and a third piezoelectric structure;

wherein the third piezoelectric structure comprises a top surface, a bottom surface, a first side, a first end coupled to the substrate, and a second end suspended away from the substrate and the first end;

Wherein the second end of the third cantilever is suspended away from the substrate and configured to deflect out of the plane of the piezoelectric layer in response to acoustic pressure;

Wherein the first cantilever beam is positioned adjacent to the third cantilever beam and separated by a gap between a second side of the first piezoelectric structure and the first side of the third piezoelectric structure, wherein a second corner of the first end of the first cantilever beam coupled to the substrate is separated from a corner of the first end of the third cantilever beam coupled to the substrate by a second initial gap distance.

30. The MEMS transducer of claim 28 further including a plurality of cantilevers, each cantilever including a corresponding protrusion and a corresponding piezoelectric structure, wherein each corresponding piezoelectric structure includes a corresponding second end suspended away from the substrate and a corresponding first end attached to the substrate, wherein each cantilever of the plurality of cantilevers is separated from a first adjacent cantilever by a first corresponding gap and from a second adjacent cantilever by a second corresponding gap, wherein the plurality of cantilevers and the associated gap between the plurality of cantilevers enclose a symmetrical polygon, wherein each corresponding piezoelectric structure has the same triangular shape in a shared piezoelectric layer.